Incidentally, Yiddish is essentially Mittelhochdeutsch (middle high german) with words basteled in from Hebrew, and turned into a dialect. Jews had traditionally lived in the urban centers of middle Europe, but were kicked out in the 13th and 14th centuries. Living in their isolated communities, their language of course developed a life of its own, and continued as a lingua franca for jews even when they were allowed back into cities. Yiddish was written in hebrew script for no other reason than that there wasn't hardly anybody to read their writing anyway. Even nobles in those days were illiterate, and only the priesthood would have been able to read, a group of people who the jews probablly had no interest in informing. The average jew was literate centuries before the average European, partially because of Talmudic study, and partially because they had to be able to keep records.
Also, a lot of yiddish words made their way into both German and Polish, some of those words have been purged, along with the people that brought them. An example of a word that's still in the German language is schleppen. The swearword Schmuck itself comes from the word schmecken. A great deal of both German and Polish food and culture is actually Jewish, unknown to Germans and Poles.
Growing up, I actually thought Putz meant the foreskin of the penis. I never actually spoke yiddish, but I learned to understand it, as my grandparents used it as a secret language. The implication I thought was that since the foreskin is the one thing Jewish men don't have, it was a double insult: secondly to equate you with a gentile, and firstly to imply that you are a disgarded piece of useless flesh from the penis. But of course I may have misunderstood, or since it's a slang word, it may have many meanings. None of those is really that appropriate to call Mr. Puts, however much of a putz or shill he may be.
Incidentally, since I'm on the history lesson anyway, I might as well point out that not all jews understand Yiddish; besides the obvious examples of jews who never learned it, there are the Sephardim: the jews who came from Spain, and were ejected in 1492, the same year as the Moors. Those jews had spoken the same Spanish as all Spaniards, with the exception that jews included jewish slang. It's an interesting history lesson for linguists to look at Sephardic and Yiddish, because both dialects are very similar, except their added slang words, to medieval Spanish and German, and are also very similar to dialects still found in some mountain towns in Spain and Switzerland.
An example anecdote about the similarity of the dialects of Yiddish and Swiss German is when my grandmother called the wife of one of my professors once...a family friend. My grandmother spoke little to no English, and the woman spoke no Russian. My grandmother knew however from her days in a concentration camp that Bavarian dialect, and even more so Swiss was very similar to Yiddish; since my professor's wife had gotten her doctorate in linguistics in Switzerland, they were able to have an interesting conversation, and one that the professor's wife told me was very surreal, since they were both essentially speaking centuries old dialects, from which modern German derived.
